Add AI Quick Quote widget and inline customer reassignment

- New AI Quick Quote floating button: staff type a verbal description to
  get an instant price estimate for phone/walk-in customers; detected
  color names are fuzzy-matched against inventory for stock status;
  saves draft quote under a Walk-In / Phone customer with one click
- Inline customer change on Quote Details and Job Details: always-visible
  native select with inline confirmation banner (no TomSelect dependency);
  ChangeCustomer AJAX endpoints on QuotesController and JobsController
- Quote Edit page: customer dropdown is now editable (lock removed)
- Fix AutoMapper missing CatalogCategory -> UpdateCategoryDto mapping
  that caused a crash on the catalog category Edit page
- Help docs and AI knowledge base updated for all three features

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/PowderCoating.Web/Program.cs

@@ -194,6 +194,7 @@ builder.Services.AddScoped<IProfilePhotoService, ProfilePhotoService>();
 builder.Services.AddScoped<IJobPhotoService, JobPhotoService>();
 builder.Services.AddScoped<IQuotePhotoService, QuotePhotoService>();
 builder.Services.AddScoped<IAiQuoteService, AiQuoteService>();
+builder.Services.AddScoped<IAiQuickQuoteService, AiQuickQuoteService>();
 builder.Services.AddSingleton<IAiUsageLogger, AiUsageLogger>();
 builder.Services.AddScoped<IAiSchedulingService, AiSchedulingService>();
 builder.Services.AddScoped<IAccountingAiService, AccountingAiService>();